Field of the Invention
The present invention relates to an imaging device and an imaging system.
Description of the Related Art
In a single-plate type imaging element, color filters (CF) through which specific wavelength components, for example, lights of respective colors of red (R), green (G), and blue (B) pass are arranged in a particular pattern on pixels in order to obtain a color image. As a CF pattern, those having a so-called Bayer arrangement are widely used. Further, in addition to a CF of RGB, there is a growing use of a CF of an RGBW arrangement that includes W pixels having a filter that transmits light in the entire wavelength range of visible light.
Japanese Patent Application Laid-Open No. 2011-055038 discloses a method of interpolating and calculating luminance values of RGB pixels from luminance values of W pixels around the RGB pixels in an imaging element having the RGBW-arranged CF. Further, Japanese Patent Application Laid-Open No. 2011-055038 discloses a method of calculating RGB values in each pixel of RGB pixels and W pixels based on a ratio of the color value and the luminance value in the pixels of interest. Further, Japanese Patent Application Laid-Open No. 2008-022521 discloses a method of calculating the value of a W pixel from the peripheral color pixels when the W pixel is saturated in an imaging element having a CF with RGBW arrangement.
When a spot light such as a star in the sky or a distant light in the city is captured, however, a light may enter a color pixel of a certain color but no light may enter a color pixel of another color. In such a case, in the method disclosed in Japanese Patent Application Laid-Open No. 2011-055038, a color ratio suitable to each pixel cannot be acquired, which may case false color. Further, it is difficult to acquire an appropriate luminance value of a saturated W pixel by the method disclosed in Japanese Patent Application Laid-Open No. 2008-022521. Also in this case, a color ratio suitable to each pixel cannot be acquired, which may cause false color.